Base
/);
-=head1 NAME
+=head1 NAME
DBIx::Class::Relationship - Inter-table relationships
=head1 SYNOPSIS
+ MyDB::Schema::Actor->has_many('actorroles' => 'MyDB::Schema::ActorRole',
+ 'actor');
+ MyDB::Schema::Role->has_many('actorroles' => 'MyDB::Schema::ActorRole',
+ 'role');
+ MyDB::Schema::ActorRole->belongs_to('role' => 'MyDB::Schema::Role');
+ MyDB::Schema::ActorRole->belongs_to('actor' => 'MyDB::Schema::Actor');
+
+ MyDB::Schema::Role->many_to_many('actors' => 'actorroles', 'actor');
+ MyDB::Schema::Actor->many_to_many('roles' => 'actorroles', 'role');
+
+ $schema->resultset('Actor')->roles();
+ $schema->resultset('Role')->search_related('actors', { Name => 'Fred' });
+ $schema->resultset('ActorRole')->add_to_roles({ Name => 'Sherlock Holmes'});
+
+See L<DBIx::Class::Manual::Cookbook> for more.
+
=head1 DESCRIPTION
This class provides methods to set up relationships between the tables
my $fredsbooks = $schema->resultset('Author')->find({ Name => 'Fred' })->books;
-Each relationship sets up an accessor method on the
+Each relationship sets up an accessor method on the
L<DBIx::Class::Manual::Glossary/"Row"> objects that represent the items
of your table. From L<DBIx::Class::Manual::Glossary/"ResultSet"> objects,
-the relationships can be searched using the "search_related" method.
+the relationships can be searched using the "search_related" method.
In list context, each returns a list of Row objects for the related class,
in scalar context, a new ResultSet representing the joined tables is
returned. Thus, the calls can be chained to produce complex queries.
will produce a query something like:
- SELECT * FROM Author me
+ SELECT * FROM Author me
LEFT JOIN Books books ON books.author = me.id
LEFT JOIN Prices prices ON prices.book = books.id
WHERE prices.Price <= 5.00
all without needing multiple fetches.
Only the helper methods for setting up standard relationship types
-are documented here. For the basic, lower-level methods, see
+are documented here. For the basic, lower-level methods, and a description
+of all the useful *_related methods that you get for free, see
L<DBIx::Class::Relationship::Base>.
=head1 METHODS
=head2 belongs_to
# in a Book class (where Author has many Books)
- My::DBIC::Schema::Book->belongs_to(author => 'Author');
+ My::DBIC::Schema::Book->belongs_to(author => 'My::DBIC::Schema::Author');
my $author_obj = $obj->author;
$obj->author($new_author_obj);
-Creates a relationship where the calling class stores the foreign class's
+Creates a relationship where the calling class stores the foreign class's
primary key in one (or more) of its columns. If $cond is a column name
instead of a join condition hash, that is used as the name of the column
holding the foreign key. If $cond is not given, the relname is used as
the column name.
+Cascading deletes are off per default on a C<belongs_to> relationship, to turn
+them on, pass C<< cascade_delete => 1 >> in the $attr hashref.
+
NOTE: If you are used to L<Class::DBI> relationships, this is the equivalent
of C<has_a>.
=head2 has_many
# in an Author class (where Author has many Books)
- My::DBIC::Schema::Author->has_many(books => 'Book', 'author');
+ My::DBIC::Schema::Author->has_many(books => 'My::DBIC::Schema::Book', 'author');
my $booklist = $obj->books;
my $booklist = $obj->books({
name => { LIKE => '%macaroni%' },
{ prefetch => [qw/book/],
});
my @book_objs = $obj->books;
+ my $books_rs = $obj->books;
+ ( $books_rs ) = $obj->books_rs;
$obj->add_to_books(\%col_data);
columns. You should pass the name of the column in the foreign class as the
$cond argument, or specify a complete join condition.
+Three methods are created when you create a has_many relationship. The first
+method is the expected accessor method. The second is almost exactly the same
+as the accessor method but "_rs" is added to the end of the method name. This
+method works just like the normal accessor, except that it returns a resultset
+no matter what, even in list context. The third method, named
+C<< add_to_<relname> >>, will also be added to your Row items, this allows
+you to insert new related items, using the same mechanism as in
+L<DBIx::Class::Relationship::Base/"create_related">.
+
If you delete an object in a class with a C<has_many> relationship, all
-related objects will be deleted as well. However, any database-level
-cascade or restrict will take precedence.
+the related objects will be deleted as well. However, any database-level
+cascade or restrict will take precedence. To turn this behavior off, pass
+C<< cascade_delete => 0 >> in the $attr hashref.
=head2 might_have
- My::DBIC::Schema::Author->might_have(psuedonym => 'Psuedonyms');
- my $pname = $obj->psuedonym; # to get the Psuedonym object
+ My::DBIC::Schema::Author->might_have(pseudonym =>
+ 'My::DBIC::Schema::Pseudonyms');
+ my $pname = $obj->pseudonym; # to get the Pseudonym object
Creates an optional one-to-one relationship with a class, where the foreign
class stores our primary key in one of its columns. Defaults to the primary
If you update or delete an object in a class with a C<might_have>
relationship, the related object will be updated or deleted as well.
Any database-level update or delete constraints will override this behaviour.
+To turn off this behavior, add C<< cascade_delete => 0 >> to the $attr hashref.
=head2 has_one
- My::DBIC::Schema::Book->has_one(isbn => ISBN);
+ My::DBIC::Schema::Book->has_one(isbn => 'My::DBIC::Schema::ISBN');
my $isbn_obj = $obj->isbn;
Creates a one-to-one relationship with another class. This is just like
=head2 many_to_many
- My::DBIC::Schema::Actor->many_to_many( roles => 'actor_roles', 'Roles' );
+=over 4
+
+=item Arguments: $accessor_name, $link_rel_name, $foreign_rel_name
+
+=back
+
+ My::DBIC::Schema::Actor->has_many( actor_roles =>
+ 'My::DBIC::Schema::ActorRoles',
+ 'actor' );
+ My::DBIC::Schema::ActorRoles->belongs_to( role =>
+ 'My::DBIC::Schema::Role' );
+ My::DBIC::Schema::ActorRoles->belongs_to( actor =>
+ 'My::DBIC::Schema::Actor' );
+
+ My::DBIC::Schema::Actor->many_to_many( roles => 'actor_roles',
+ 'role' );
+
+Creates a accessors bridging two relationships; not strictly a relationship in
+its own right, although the accessor will return a resultset or collection of
+objects just as a has_many would.
+
+To use many_to_many, existing relationships from the original table to the link
+table, and from the link table to the end table must already exist, these
+relation names are then used in the many_to_many call.
+
+=head3 Created accessors
+
+=head4 $rel
+
+ my $role_rs = $actor->roles;
+
+ my $role1 = $actor->roles({ name => 'role1' })->first;
+
+Returns a resultset for the table on the far-right side of the many-to-many
+relationship. (e.g., in the above example, a CD's producers).
+
+=head4 add_to_$rel
+
+ my $role = $schema->resultset('Role')->find(1);
+ $actor->add_to_roles($role);
+ # creates a My::DBIC::Schema::ActorRoles linking table row object
+
+ $actor->add_to_roles({ name => 'role1' });
+ # creates a new My::DBIC::Schema::Role row object, as well as the
+ # linking table object
+
+Adds a linking table object for the specified object, or if a hash is given
+instead the related object is created before the linking table object is
+created.
- ...
+=head4 remove_from_$rel
- my @role_objs = $actor->roles;
+ my $role = $schema->resultset('Role')->find(1);
+ $actor->remove_from_roles($role);
+ # removes $role's My::DBIC::Schema::ActorRoles linking table row object
-Creates an accessor bridging two relationships; not strictly a relationship
-in its own right, although the accessor will return a resultset or collection
-of objects just as a has_many would.
+Removes the link between the current object and the related object. Note that
+the related object itself won't be deleted unless you call ->delete() on
+it. This method just removes the link between the two objects.
=cut
projects / dbsrgits/DBIx-Class.git / blobdiff